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H3 Transfer Case Issue - No Front Drive?

Steve #1

Well-Known Member
Messages
534
Location
TEXAS
Question for those that have more intimate knowledge of the H3 transfer case than I do.

Driving in to work on the freeway tonight I hit a little bump in the road, heard a little clunk and a rattle then my RPMs shot up and had no power to the wheels. After coasting off the road I found I had no power at all to the wheels but no crazy sounds or vibrations. When I locked the transfer case in 4HI, I had power. I took it easy up the access road looking for a parking lot and it didn't drive like anything was wrong. Rather than being late for work I chanced it and drove the rest of the way in.

So far, my trouble shooting has been limited but the feel while turning makes me think the front drive is out. In 4 high open unlocked in gear, neither shaft is turning.

Any trouble shooting suggestions would be appreciated.
 

boe

Member
Messages
17
Location
Germany
This problem can be caused by broken

- half or drive shaft
- front or rear differential

When you're in 4locked the power is transmitted to front and rear without a differential allowing them to have different rpm.

You can check what's broken (2nd person needed):

- switch to 4HI unlocked and drive mode (parking brake applied)
- look if one of the drive shafts ist revolving

If yes - that's the broken side.
 

4speedfunk

Well-Known Member
Messages
4,197
Location
Tardville
Yep...boe is dead-on. If the truck moves in 4HI-lock and not in 4HI-street....its a break in the driveline. Your symptoms sound like a typical front diff failure. Like boe suggested...put the t-case in 4HI-street and have a buddy look underneath, while you give it some slight throttle. If the front driveshaft (input) is spinning...and neither front half-shaft (output) is turning...then you have a smoked front diff. To confirm the condition, pull the front diff cover and check the teeth on the gears and also the magnetic drain plug. If it looks like a chia pet, its time for a complete teardown & rebuild. Very common. Very expensive. $500-$2500 depending mostly on labor.

Sometimes you can have a broken CV joint on one of the half-shafts. Given the fact that you hit a bump, and then heard the rattle...its very likely, its nothing more than a CV joint failure. If this is the case, you should be able to see at least some of the half-shaft turning, and it will be obvious if the CV joint has failed. The boot will be destroyed, and there will be grease everywhere. If you do find a broken CV joint...consider yourself lucky. This is an easy and inexpensive repair. You should buy two new CV shafts and output seals, and do both sides...you'll be good for another 60k-100k. Many H3 guys do this repair themselves. It will cost $300 in parts and up to $800, if you have to pay labor.

I'm not ruling out a rear diff failure but these are extremely rare. I would look hard at the front end since they are famous for such failures.
 

Steve #1

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Messages
534
Location
TEXAS
OK, I did some more testing.

The front half shafts are fine. Last time I broke one it took out the brake lines. I wouldn't have continued driving if I there was any chance that was the issue. :whaa:

With one or both front tires off the ground spinning the tire turns the front prop shaft with a ticking sound at the t-case regardless of t-case mode (I didn't try 4lo) or trans in or out of gear.

With all 4 tires off the ground in 4H open rear wheels can be turned by hand with trans in gear rear prop shaft turns front does not (don't know if it should).

With all 4 tires off the ground in 4H locked rear wheels can not be turned by hand with trans in gear.

With all 4 tires off the ground in 4H open engine power in 1st gear nothing turns (stabillitrac off and TC over ridden).

With all 4 tires off the ground in 4H locked engine power in 1st gear rear wheels turn (stabillitrac off and TC over ridden).

I tried some other combinations too but pretty much determined that the front end isn't getting power and the rear is only getting power with the t-case locked.
 

4speedfunk

Well-Known Member
Messages
4,197
Location
Tardville
Tires off the ground?...not sure that will tell u much. There is no resistance to induce the problem.
Put it in 4HI-street...on the ground...in DRIVE...and give it some throttle. Have someone check the front driveline. If the front diff is broke, the truck will not move. The front driveshaft will spin and grind the broken parts into dust....it will be very obvious.
 
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Steve #1

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Messages
534
Location
TEXAS
That was in my first post. I guess it wasn't clear the way I wrote it, 4H unlocked in gear under power, neither prop shaft turns.

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boe

Member
Messages
17
Location
Germany
4speedfunk is right, tires off the ground doesn't help much.

When testing in 4HI locked with engine on and 1st gear in: Did the front driveshaft revolve?

I not: Something inside the transfer case is broken.

If yes: Did one of the half shafts revolve (without turning the wheel)?

If yes: This half shaft is broken.

If no: Front diff is broken.


Edit: Your transfer case is gone...
 
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Steve #1

Well-Known Member
Messages
534
Location
TEXAS
Yes, in 4HI locked with the engine on and in first gear the front prop shaft revolves when the vehicle moves.
The reason I tested with the wheels off the ground was to determine if the shaft was being turned by the case or by the wheels (it was turning because the wheels were turning).
I am pretty sure the problem is in the case but I am not familiar enough with how the case works to pinpoint where the failure could posibly be. Due to the cost of some of the internal parts it isn't practical to replace them vs replacing the entire case. But some parts are worth replacing.

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boe

Member
Messages
17
Location
Germany
The 4HI locked test I mentioned was for wheels off the ground.

4HI unlocked and no drive shaft revolves means: Transfer case broken (diff).

Maybe you can get a rebuild case in exchange for your broken one somewhere.
 

Steve #1

Well-Known Member
Messages
534
Location
TEXAS
Gotcha, no, front drive shaft didn't turn, just the rear. It seems prices have gone up on the cases, but replacing it would be a good excuse to upgrade to an NR6. The question then is to get a new one or a junkyard one. With this being my second T-case in 130K miles I'm leaning to the new side.

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boe

Member
Messages
17
Location
Germany
Just this simple:

No power transmission to front wheels (from t-case). Something inside t-case broken.
 

4speedfunk

Well-Known Member
Messages
4,197
Location
Tardville
Oh. Its broken. Now I get it. Seem so clear when you put it that way. -LOL

Seriously, it could be any number of things. I still find it interesting that the issue happened when you hit a bump in the road. That sounds a lot like something was loose and lying in the bottom of the t-case and got bounced up and into the rotating assembly. I say this because I have seen several instances where the snubber plate was completely separated from its mounts, and flopping around inside the case. Its really hard to say what causes a t-case to fail but, obviously...ANYTHING loose inside the case will cause instant chaos. The snubber always seems to be the first thing that falls out on the floor, when I take one apart.

There are two small Torx-headed screws that hold it in place (photo #1), and these (like all things on the H3) are woefully undersized. They tend to pull out of the casting. So I remedy the problem with big, fat, 1/4-20 studs (photo #2). And I also add nylon locknuts and Loc-tite to keep things where they are supposed to be (photo #3). Snubbers were added in 08 I think...early t-cases don't have them (not sure what year Steve's H3 is). Last pic shows the before and after...
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I'm not saying this is the problem but, the bump in the road causing the drive system to suddenly break free from the motor rpms....seems to point to loose parts inside the case. Perhaps something got flipped up and into the chain...and BOOM...tow-truck time.
 

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4speedfunk

Well-Known Member
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4,197
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Tardville
To clarify...the t-case in the photos got a new chain, new snubber, a Dorman shift fork, and a good cleaning with solvent. Despite the carnage...the gears, bearings, and internals all seemed to be in great shape. So it was a fairly cheap fix, compared to replacing the entire unit. This was a 3394 (NR6) 4:1 case.

Also, this case never totally loss drive in 4HI-Street. That makes me think Steve's problem may be more severe.
 

Steve #1

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534
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Yes, I think broken would be the appropriate technical term. To make to truck go I can put it in 4HI locked and the rear wheels will drive the truck. Other than a little more gear noise from the t-case, like you normally get when it's locked, it doesn't sound like there is any carnage going on inside the case (not that I plan on chancing it any more). The bump I hit is just a small dip in the pre-fabed highway interchange it isn't something you normally notice unless you hit it 4-5 times a week at 70MPH like I do. The noise sounded like running over a small bit of mettle, but I had the radio on loud enough to hear it over the M/Ts and the RPMs shot up at the same time.

The entire transfer case was replaced following the initial HUMMER shutdown which I guess was in late 2009. I had to wait a month to get it because BW had stopped making them. When mine was built BW could only hope that GM would maybe pay them for the cases at some point. The front output shaft was replaced maybe a year later due to a vibration. I have a feeling the front output shaft is at fault this time too, but that is pure speculation, because other than looking at the parts diagram, i don't know how it is put together.

I'd love to hear any speculation you may have on the front output shaft as the possible culprit.
 

4speedfunk

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4,197
Location
Tardville
I'm afraid anything I could ad would be exactly that....speculation. Even the snubber thang is speculation. If you are 100% positive its the transfer case, then you should drop it, and have a closer look. Other than being quite heavy, there is not much to pulling it. Once you have it out from under the truck, give it a good shake and roll it around. If something is seriously wrong...you'll hear small parts clanking around inside before you even take it apart. I've not had one that lost an entire mode like yours. I've heard of front output issues but, I've not seen any evidence of this with the ones I've had apart.

You can download a rebuild PDF from Schwarttzy.com and I recommend reading it front to back about five times before you open it up. Its not near as intimidating as it looks. You'll need a chain and tranny-to-transfer gasket at the very minimum. I always spring another $20 for an aluminum shift fork (stock is plastic)...might as well since you got it apart. Once you get inside it...you may find you need other parts. I get most of my t-case parts direct from borg-warner and a few other small items from GM.

The BW3393/3394 must have fresh fluid. I mean FRESH. Like every 20K miles. For some reason they seem really finicky about fluid changes. (My 99 Burb with an NP246 has 200K on original fluid).
 

jakesz28

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Messages
1,037
Location
Cabool MO
Does the plastic part of the locking collar ever wear out with the aluminum shift fork installed?

After this I may keep a few parts in the garage should I have to open one of these up again. Like the $40 shaft for the internal shift control. Poor design with that 1/8" hardened shaft pushed in it.
 

JPaul

Well-Known Member
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2,400
Location
Way up north, UT
I'm sure it wears out eventually, it'd still wear out with the plastic fork (if the fork didn't wear out first every time). Everything wears out given enough time and lack of lubrication. I don't think you'll really see excessive increased wear though, not enough to make a huge difference in how long the transfer case lasts.
 

Steve #1

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534
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TEXAS
Since I can't get my 3 in the garage and it threatened to rain all last weekend I haven't made any progress. After thinking more about what happened and how the case works, I think the chain may have broken and I just got lucky that nothing got bound up. My plan was to pull the case and if it was just the chain, replace it and be happy it wasn't worse. Anything over the $300 or so replacing the chain would cost me and I could justify upgrading to a 3394. Rockauto has reasonably priced rebuilt units provided they would take my 3393 core. I was also keeping my eyes on the local wrecking yards for a 3394.
I got "lucky" and found a 3393 on craigslist that I got for $300. I'm a little bummed about not getting the 3394 but it was to hard to pass this deal up. The guy I bought it from pulled it from his 07 in perfect working order when he swapped it for a 3394. As long as I get the gasket, and I guess the seal, I should be able to have it up and running Saturday.
 

odwah

Member
Messages
23
Location
Michigan
I don't know if this was mentioned or ruled out, but could it be your CV that connects to your TC on the front drive shaft? Sounds like what happened to me the other day, and that part had failed. Popped a new one on and good as new!
 

Steve #1

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Messages
534
Location
TEXAS
New case is in and it's working like a champ. It has a mid '05 build date with the low fill hole.:gaah: I'm sure this also means it has the plastic shift fork. I thought about swapping the shift fork but decided to just get it in. The bad case had some kind a fancy black sparkly fluid in it. :emb: The little bit of fluid that was in the bottom of the new case looked to be in very good shape. I refilled it with Royal Purple ATF.

Taking the case out wasn't that bad. Fighting gravity and putting it back in was a PITA even using a tranny jack, but I found a trick to make it easier. I used 3 ratchet straps run over the frame rails and under the case to lift it up. With the straps positioned right you can even get the front output to drop down in to position. I only had to lift it about an inch to get it lined up. I'm sure some guys could just lift it up, but sometimes us littler guys have to work smart. :)

I'll follow up if I decide to crack the old case open to see how bad the carnage is.

Thanks to everyone for your input on this.
 

Scarsman

Sponsor
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1,561
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Monroe, WA
Well, you HAVE to open the case! You can't just let this go! We gotta know what happened inside!

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